In certain mixes, such as tread mixes, silica has long been used instead of conventional carbon black as a reinforcing filler, because of the advantages of silica in terms of rolling resistance and wet road-holding capacity.
Silica is used in combination with silane bonding agents, which, by bonding with silanol groups, prevent the formation of hydrogen bonds between silica particles and, at the same time, clinch the silica chemically to the polymer base.
Recent findings show trialcoxymercaptoalkyl-silanes to be excellent silane bonding agents in terms of reducing rolling resistance and hydrocarbon emissions.
The formula I compound is the one which affords the best advantages.SH(CH2)3SiR1R22  (I)
where
R1 is —OCH2CH3 and
R2 is —O(CH2CH2O)5(CH2)13CH3 
Alongside the above advantages, however, trialcoxymercaptoalkyl-silanes have the drawback of impairing processing of the mix, and attempts to solve the problem have only resulted in impairing other characteristics of the mix, such as abrasion resistance and elasticity.